In recent years, a direct chip attach system using a bare chip such as a semiconductor element flip chip or the like is drawing attention. A so-called “C4 technique” is famous as the connection method for this flip chip system, in which a high melting point solder bump is formed on the chip side, and intermetallic bonding with solder on the ceramics circuit substrate-side is carried out.
However, when a resin-based substrate such as a printed circuit substrate made of glass and an epoxy resin is used instead of the ceramics circuit substrate, it poses a problem such as insufficient connection reliability due to breaking of the solder bump bonding part caused by a difference in coefficient of thermal expansion between the chip and the resin-based substrate. As a countermeasure for such a problem, it is general to carry out a so-called underfill which is a technique in which the reliability is improved through the dispersion of thermal stress by filling the gap between the semiconductor element and the resin-based circuit substrate using, for example, a liquid resin composition.